I hardly think that "FA" is “extremely” offensive, nor it’s close cousin “FO” for that matter. While it may not be the most pleasant of terminology, I certainly wouldn’t label it as “extremely” offensive.

Our over sensitivity to such things IMHO is more evidence of the namby pamby overtly PC correct nuttyness that has gripped the world of today. There’s nothing wrong with a couple of well placed “F’s” & often it is the only way to drive home a point or illicit action. Also a well placed “F” can be quite humorous too, in the correct circumstances